1. “ Decay & snapback in main LHC dipoles vs injection current”, LUMI-05, Arcidosso, 1 September 2005, marco.buzio@cern.ch Page 1/4 During ramps, boundary-induced coupling currents (BICCs) are induced in the LHC cable creating a field ripple with period  twist pitch length BICCs diffuse along the cable during stationary excitation with time constants  1000 s, leading to demagnetization of allowed harmonics of the order of a few units (decay) As soon as current ramping is resumed, the field snaps back to (almost) the previous hysteresis curve with an exponential law vs. magnet current Decay and snapback amplitudes depend to some extent upon all cycle parameters, mostly: - increase (~linearly) with pre-cycle flat-top current - increase with pre-cycle flat-top duration - decrease with pre-injection duration Dynamic field effects in main LHC dipoles

2. “ Decay & snapback in main LHC dipoles vs injection current”, LUMI-05, Arcidosso, 1 September 2005, marco.buzio@cern.ch Page 2/4 Decay and snapback in model LHC dipoles vs. injection current Parametric study carried out on 1 m long model magnet shows no clear evidence of the dependence of absolute harmonic effects vs I inj

3. “ Decay & snapback in main LHC dipoles vs injection current”, LUMI-05, Arcidosso, 1 September 2005, marco.buzio@cern.ch Page 3/4 Decay and snapback in main LHC dipoles vs. injection current Absolute B3 decay: reduction of 15% from 0.45 TeV to 1 TeV injection (influence of longer ramp to injection not taken into account)

4. “ Decay & snapback in main LHC dipoles vs injection current”, LUMI-05, Arcidosso, 1 September 2005, marco.buzio@cern.ch Page 4/4 Normalized B3 decay: reduction of a factor 2.6 from 0.45 TeV to 1 TeV injection Decay and snapback in main LHC dipoles vs. injection current